Percussion drilling tool



June 18, 1968 s. COLLIER 3,388,636

PERCUSSION DRILLING TOOL Filed Oct. 18, 1965 damue/ A. (a ///e/' INVENTOR.

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ATTQRNEV United States Patent 3,388,636 PERCUSSKGN BRELLING TUOL Samuel L. (Iollier, Houston, Tern, assignor to Mission Manufacturing Company, Houston, Tex a corporation of Texas Filed Get. 18, 1965, er. 1 o. 497,494 2 Claims. (U. 91-234) ABSTRACT 01* THE DISCLGSURE A downho-le type of percussion drilling tool is supported by telescoped members in the drill string so that the percussion tool may be relieved of the entire weight of the drill string and thus may rely solely upon the percussion force in its drilling action. This enables the use of very high drilling pressures with consequent high drill pipe weights applying such reactive weight to the drill.

This invention relates to percussion drilling apparatus and consists particularly in novel means for preventing unwanted diversion of the hole being drilled by relieving the bit of the weight of the heavy driil collars customarily mounted on the drill between the same and the supporting drill string.

One of the advantages of percussion drilling of rock formations is that the heavy drill collar weighting of the bit, as in conventional rotary drilling, may be at least partly avoided, However, with the use of a percussion drill as shown, for instance, in Bassinger et a1. Patent No. 2,859,733, it has been necessary, in order to hold the motor casing seated on the bit or anvil and maintain the bit firmly seated against the hole bottom during the power stroke of the piston, to mount such heavy drill collars just above the drill motor and between the same and the supporting drill pipe string. This is because the reactive fluid pressure exerted downwardly on the piston during the power stroke also acts upwardly against the motor casing, tending to separate the casing from the anvil. In order to keep the motor running uniformly, it is necessary to maintain a predetermined relationship between the anvil and easing back head. The greater the pressure of the operating fluid used, the greater this weight of drill collars must be and, consequently, it has been impractical, heretofore, to utilize operating fluid pressures more than on the order of 200 or 250 pounds per square inch. While such limitation in the operating fluid pressure necessarily limits the eificiency of the percussion motor which operates the drill, any substantial increase of drill collar weight, as is necessary to accorn modate higher operating fluid pressures, results in excessive hole diversion or drift as well as hard dragging of the bit on the hole bottom during indexing. This is because the straightness of the hole is affected by inclined formations and other anomalies and the effect of such anomalies is enhanced where greater drill collar weights are used.

Accordingly, it is an object of the present invention to reduce as far as possible the weight applied to the drill bit through the percussion motor casing, as distinguished from the percussive power applied through the hammer piston.

A more detailed object is to relieve the percussion drill of the weight of the drill string.

Still another object is to provide a percussion drill and supporting drill pipe string combination in which the upward reactive force of the operating drill fluid is largely carried by the drill string independently of the drill itself, the drill string, of course, being weighted as necessary to properly resist these upward reactive forces.

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According to the present invention, these objects are achieved substantially by incorporating a splined slip joint between the percussion drill casing and the lower end of the supporting drill pipe string. Suflicient drill collars are incorporated at the lower end of the drill pipe string to maintain the string properly suspended and to prevent the string from being forced upwardly by the reactive force of the drill operating fluid during the forward working stroke of the piston. However, the drill collar weighting is not applied to the bit. Thus, it is possible to utilize operating fluid pressures of 500 p s.i. or more without excessive weight on the bit and resultant hole diversion, as would be the case if such operating fluid pressures were utilized with current forms of percussion drill and supporting drill pipe assemblies. Preferably, the inner area of the splineway-slip joint is not less than a slight amount less than the area of the upward working face of the percussion motor piston so that substantially all of the motive fluid reaction is carried by the drill string and not more than a small portion thereof is applied to the motor casing.

In the accompanying drawings which illustrate the invention,

FIG. 1A is a vertical center section through the upper portion of a drill pipe string-slip joint-percussion motor assembly illustrating the invention; and

PEG. 1B is a similar view showing the continuation lower part of the percussion motor.

At the lower or forward end of the drilling tool there is provided a rock bit 5 of any suitable design which may be secured to an anvil 7 by a threaded connection 6, or formed integral therewith. The anvil has splineways 5% receiving roller-type splines 9 which are accommodated in matching splineways in a split nut 10 threaded into the lower end of percussion motor casing 11. The percussion motor casing has an enlarged lower working chamber part 12 and a reduced upper working chamber part 13 which slidabiy receive similarly-shaped and proportioned parts 14 and 15 of the hammer piston. A spider 16 mounted in the casing above the piston supports an axial tube 17 which depends through a finger 31 and a somewhat larger axial passage 18 in the piston, tube 17 extending through a finger-like boss 22 which projects from the bottom surface 19 of the piston. Passage 18 communicates through inclined passages 20 with grooves in the undersurface of the piston. The reduced upper surface 21 of the piston is exposed to the operating fluid through spider 16.

Mounted in the casing above spider 16 is a second spider member 25 carrying a central apertured part 26 which slidably receives the stem 27 of a float valve 28 urged upwardly by a coiled spring 29 to seat against a valve seat forming shoulder 3i) in the casing. At the upper end of the casing is a threaded pin 31a which, in effect, forms a connection for the operating fluid supplied through a drill pipe string extending upwardly through the bore and having at its lower extremity drill collars, one being shown at 32, of adequate weight, as will be described.

Projecting below drill collar 32 is a tube 35 which forms the inner part of a slip joint. As such, it has splines 36 on its lower portion slidably received in matching splineways 37 on the inner confronting wall of a tubular member 38 which has a threaded box 39 at its lower extremity receiving pin 31 at the upper end of than the area of the upper working face 21 of the hammer piston, which, in this case, is assumed to be less the area of hole 18. This insures that most of the upward reactive force of the operating fluid applied to the hammer piston will affect only the suspended drill string and drill collars while only a small part of this reactive force, as represented by the product of the working fluid pressure and the transverse area of shoulder 30, will tend to lift the casing, for instance, for just supporting the casing. In the drawing, shoulder 30 is exaggerated for clarity. However, the area may be greater than area 21 so that some of the reactive force of the operative fluid will be applied to the casing and bit in addition to the percussive force applied by the differential hammer piston.

In operation of the invention, as the percussion tool at the end of a drill pipe string is lowered into the well bore, the splineway-slip joint will, of course, be fully extended, supporting the drill tool, and the anvil-bit combination 7, will be in its inoperative extended position. As the bit strikes bottom, the casing will lower until the anvil-bit is fully collapsed in the casing and the lower extremity of the casing (split nut 10) rests upon the bit. Thereafter, the operator will continue to lower the drill pipe string until only a slight clearance remains between the drill collars and the upper end of slip joint outer member 38. The operating fluid may then be turned on and the drill pipe string, slip joint, and percussion motor rotated, as is customary in percussion drilling. Due to the almost complete elimination of drill string weight on the bit in the preferred form, I have found that the hole direction may be much more readily controlled than has been the case heretofore where heavy drill collars have been applied to the drill and bit. Moreover, I am able to increase the operating fluid pressure to as much as 500 p.s.i., thus achieving marked operating efliciencies, without loss of hole direction control.

The percussion motor shown is of the differential piston type, the operation of which is explained more fully in the above-mentioned Bassinger et al. Patent No. 2,859,733. However, other types of percussion motors may be substituted. Tube 17 is for the purpose of providing a constant bypass for operating fluid into the exhaust channel 7a of the anvil for augmenting the supply of chip-lifting air. Float valve 28 is normally opened during operation, but closes against its seat when the supply of operating fluid is stopped to prevent the entry of ambient drill fluid into the percussion motor. In operation of the motor, the working fluid pressure is applied constantly to the upper surface 21 of the piston portion 15. In the upper or rearward position of the piston, finger 31 is telescoped within axial piston passage 18 and substantially closes the same. As the piston descends, finger 31 emerges from passage 18, whereupon the working fluid passes therethrough to bottom pressure chamber 12., Shortly thereafter, bottom finger 22 enters exhaust passage 7a in the anvil, closing it. Since bottom surface 19 of the piston is larger than the top surface thereof, the downward motion of the piston will be arrested and, after the piston strikes the anvil, it will be driven upwardly. When finger 22 is withdrawn from passage 7a, lower motor chamber 12 will be exhausted. Shortly thereafter, upper finger 31 will again enter piston passage 18 to isolate the upper working chamber and repeat the cycle.

The invention may be modified in various respects as will occur to those skilled in the art. For instance, the anvil and bit may be made integral or separately, as shown, and other types of percussion motors may be utilized. Moreover, the slip joint, normally, will include stop means to resist disassembly of the parts, particularly during hanging of the tool. Exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. The combination in a downhole percussion drilling tool comprising a casing with a bit-supporting anvil received in the forward end thereof and a connection at the rear end thereof for operating fluid, a hammer piston reciprocable in said casing, and valving means for directing operating fluid from said connection into opposite ends of said casing and alternately exhausting said ends to cause said piston to beat upon said anvil, of a slip joint mounted rearwardly of said tool and including telescoping inner and outer parts, one forming an extension of said connection and the other being adapted for attachment of support and operating-fluid-carrying tubing, the transverse area of the confronting seal surfaces of said parts being approximately equal to the opposing transverse area of said piston so that the effect of operating fluid upon said piston areav and said seal surfaces area will substantially relieve said casing of the reactive force of the operating fluid.

2. The combination described in claim 1 in which said anvil is slidable in the forward end of said casing between its operative position collapsed within said casing and an inoperative extended position, the difference between the transverse area of said surfaces and said piston being such that when the tool is resting in drilling position on the bottom of a hole and said area and said piston are exposed to operating fluid said anvil will be maintained in its collapsed operating position in said casing.

References Cited UNITED STATES PATENTS 574,784 1/1897 Carlinet 91-434 1,570,379 1/1926 Gilrnan 91 234 3,012,540 12/1961 Vincent et al. 91- 234 3,215,210 11/1965 Dickinson 91-234 2,686,660 8/1954 Storm 321 MARTIN P. SCHWADRON, Primary Examiner.

PAUL E. MASLOUSKY, Examiner. 

